Al-Qaida is again the primary suspect in today's co-ordinated attacks on state security buildings in south Yemen, though it is hard to disentangle the activities of the jihadi group from those of a growing secessionist movement in the impoverished Arabian peninsula country.

Reports from Yemen's capital, Sana'a, described how masked gunmen firing mortars, machine guns and rocket-propelled grenades assaulted two adjoining intelligence and security offices, leaving five to 11 people dead and many wounded in Zinjibar in Abyan province.

It was the second spectacular attack by suspected al-Qaida gunmen on security premises in Yemen in less than a month. In June, the group raided the southern headquarters of the political security office in the port city of Aden, killing 11.

The growing boldness and frequency of such attacks is fuelling concern among western and Arab governments and intelligence agencies that Yemen has become a growth area for Osama bin Laden's group since it was in effect defeated in neighbouring Saudi Arabia and reconstituted itself as al-Qaida in the Arabian Peninsula (Aqap).

Last Christmas Day's abortive attack on a US-bound plane by Umar Farouk Abdulmutallab, the so-called "underpants bomber", underlined worries about the mobilisation of foreign volunteers, as did the recent appearance of an English-language online magazine published by Aqap.

In April it claimed responsibility for a failed suicide bombing attack on the British ambassador in Sana'a. The group has established relatively safe strongholds in the country's largely autonomous tribal regions and is sheltered by the unwillingness or the inability of the state security forces to operate there.

This year the US has quietly stepped up efforts to back and galvanise Yemeni government counter-terrorism measures but it is worried about an anti-American backlash after being accused of killing innocent civilians in drone attacks on alleged al-Qaida targets.

Understanding the situation in Abyan and adjoining areas is complicated by the Hiraak, a separatist movement that feeds on grievances dating back to the unification of the old north and south Yemeni states in 1990 and the civil war that followed.

Yemenis insist that their biggest problem is not al-Qaida but the Houthi rebellion in the north as well as the ineffectiveness and corruption of the central government, rapid population growth, unemployment and the depletion of both oil and water reserves. Combined, some analysts fear these factors could lead to the ultimate failure of the Yemeni state.